WHACKY SCI-FI ENERGY PROPOSALS
Any mildly observant person is bound to notice that energy plays an important role in everyday life. Look around, and it is not too difficult to find various attempts at harnessing it. Plants extract energy from the sun through photosynthesis, animals extract energy by digesting organic material, and any industrial landscape is bound to have vehicles burning fossil fuels or the odd photovoltaic cell or wind turbine making use of renewable energies.
But, despite having sought for ways of extracting energy from the environment for billions of years, life is still not at all efficient at doing so, at least not when its various attempts are compared to theoretical limits. If you want to know how much potential energy is available to be tapped, you must turn to what is probably the most famous equation in the world: E=MC^2. This equation is basically a conversion factor that calculates how much energy is contained in a given amount of mass. If you take something like a candy bar, and you multiply its mass by the speed of light squared, that tells you precisely how much energy the bar contains. The speed of light squared is a huge number (written in MPH it is 448, 900, 000, 000, 000, 000) so even a tiny amount of mass can unleash an enormous amount of energy. An atomic bomb’s nuclear explosion for example, is the result of just a small amount of uranium being converted to energy.
If you were to eat that candy bar, you would extract a mere ten-trillionth of its mc^2 energy. To put it another way, the process of digestion is only 0.00000001% efficient. Burning fossil fuels like coal and gasoline fairs a bit better, extracting 0.00000003 and 0.00000005% of the energy contained in such fuels respectively. How about nuclear fission, which, as we saw earlier, is capable of unleashing tremendous amounts of energy? Well, it certainly does a lot better than digestion or fossil fuel burning, but at an efficiency rating of 0.08%, it’s still far from ideal.
The fact that we are mostly failing to put this energy to use can be considered good news, in that any energy shortage we may experience has little to do with it being a scarce resource, and is instead due to our inability to access it. Unlike true scarcity (which we can’t do much about) an inability to access what’s available is a problem that can be addressed with appropriate technology. For example, by 2030 the world will need around thirty trillion watts, an energy need that could be met if we succeed in capturing three ten thousandths of the sun’s energy that hits the earth.
That would be a most welcome outcome in terms of securing our future, but even this achievement would not fare particularly well in terms of putting all available energy to good use. After all, most of the Sun’s output does not strike the earth but is instead dumped into empty space. Some radical thinkers have proposed ambitious schemes for harvesting this wasted energy.
THE DYSON SPHERE
One such proposal was put forward in 1960 by Freeman Dyson. His idea was to deconstruct Jupiter in order to form a spherical shell around the Sun. Doing so would enable our descendants to capture a trillion times more energy than we are capable of harvesting today. It would also provide 100 billion times more living space if you were able to move around its surface and, with the sun at the centre and you walking around on the inside of the sphere, everywhere on your habitat there would be permanent daylight. However, with gravity ten thousand times weaker than what we’re used to, travelling all the way around such a sphere without falling off would be pretty much impossible. In fact, it’s probably fair to say that life in general (or, at least, life as we know it) would be infeasibly difficult at best and impossible at worst if we had to live on the inner or outer surface of the Dyson sphere itself.
A way around that problem may be to construct habitats like the ones proposed by an American physicist called Gerard K O’Neill within the Dyson sphere. Known as O’Neill cylinders, they could provide habitats more like those we are familiar with if they orbit the sun in such a way as to always be pointing straight at it. Centrifugal force caused by their rotation could provide artificial gravity, and we could even have a 24 hour day-night cycle if there were mirrors to direct the sunlight in an appropriate way.
Obviously, constructing a Dyson sphere would be a feat of engineering way beyond anything remotely achievable today. But that didn’t stop its originator, Freeman Dyson, from considering them a realistic prospect, given sufficient time. “One should expect that, within a few thousand years of its entering the stage of industrial development, any intelligent species should be found occupying an artificial biosphere which completely surrounds its parent star”.
Amazingly, even this vastly ambitious project would not be all that successful at capturing the energy contained within the sun’s mass. This is because the process of nuclear fusion going on in a star like our Sun succeeds in converting only about a tenth of its hydrogen fuel, and after that its life as a normal star is over and it will expand into a red giant and end its life. So, even if we were to enclose the sun in a perfect Dyson sphere, we could not hope to put more than 0.08% of the sun’s potential energy (i.e the energy contained in its mass) to good use.
SPINNING BLACK HOLES
For those descendants looking for more power than even a Dyson sphere can provide, they might consider an idea put forward by a British physicist called Roger Penrose. Many black holes are spinning, and this rotational energy could potentially be put to good use. Like all black holes, the spinning variant have a singularity (the remnants of a star so dense it has crushed itself to an infinitesimal size and of which we know very little about because it exists in realms of nature beyond anything our current models can handle) and an event horizon, which is a region of space surrounding the black hole that, once crossed, nothing can escape the gravitational pull of the singularity at its centre. A spinning black hole also has another feature known as an ‘ergosphere’, where, according to Max Tegmark, “the spinning black hole drags space along with it so fast that it’s impossible for a particle to sit still and not get dragged along”.
What this means is that any object tossed into the ergosphere will pick up speed as it rotates around the black hole. Normally, such objects will inevitably cross the event horizon and be swallowed by the black hole. But Roger Penrose worked out that if you could launch an object at the right angle and have it split into two pieces, then only one piece would get eaten while the other would be escape the black hole. More importantly, it would escape with more energy than you started with. This process could be repeated for as many times as it takes to convert all of the black hole’s rotational energy into energy that can be put to work for you. Assuming the black hole was spinning as fast as possible (which would mean its event horizon was spinning at close to the speed of light) you could convert 29% of its mass into energy using this method. That would be equivalent to converting 800,000 suns with 100 percent efficiency, or having 1000 million Dyson spheres working for billions of years.
CONCLUSION
As I said before, Dyson spheres and spinning black holes are proposals way beyond anything remotely plausible today. It might be tempting, therefore, to dismiss such ideas as crazy science fiction. But, I think there is a serious point to be made among all this whacky sci-fi stuff, which is that we are extremely far from putting available energy to good use. Next time you hear about an energy crisis, bare in mind that this really has nothing to do with energy being a scarce commodity. No, it is all down to our technical inability to capture the energy that is available. These crazy sci-fi proposals are therefore something to aspire to, and even if our actual technologies succeed in only capturing one percent of one percent of the energy that something like a Dyson sphere can harvest, that would provide way, way more energy than our global needs are likely to require. And, besides, if your going to have ambitions, they might as well be big!
REFERENCES
Life 2.0 by Max Tegmark
The Singularity Is Near by Ray Kurzweil.